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The value of non-invasive techniques for the assessment of critical limb ischaemia
D T Ubbink1, I I Tulevski, D den Hartog
1Department of Surgery, Academic Medical Centre, Amsterdam, The Netherlands.
Insights
Ankle blood pressure alone is insufficient for diagnosing critical limb ischemia (CLI). Adding toe pressure and transcutaneous oxygen measurements significantly improves CLI detection, guiding necessary invasive therapies.
Area of Science:
- Vascular Medicine
- Diagnostic Imaging
- Peripheral Artery Disease
Background:
- Critical limb ischemia (CLI) diagnosis relies on clinical signs and blood pressure, but these can be non-specific.
- Existing diagnostic criteria may underestimate CLI severity, potentially delaying critical interventions.
Purpose of the Study:
- To evaluate the added diagnostic value of transcutaneous oxygen tension (pO2) and toe blood pressure measurements in identifying CLI.
- To compare these measurements against established European Consensus Document (ECD) criteria.
Main Methods:
- Prospective study of 49 patients (65 legs) with Fontaine stages III-IV CLI.
- Measurements included ankle systolic pressure, toe systolic pressure, and transcutaneous pO2.
- Surgeons were blinded to toe pressure and pO2 results; treatment decisions were recorded.
Main Results:
- Ankle pressure alone identified only 17% of legs with CLI.
- Combining ankle pressure with toe pressure and pO2 increased CLI detection to 63% (p < 0.0001).
- Toe pressure and pO2 significantly improved classification accuracy compared to ankle pressure alone, aligning closely with ECD criteria and invasive treatment needs.
Conclusions:
- Ankle blood pressure measurements have limited utility in diagnosing CLI.
- Incorporating toe pressure and transcutaneous oxygen measurements enhances the detection of CLI requiring intervention.
- These combined measures offer a more accurate assessment for guiding vascular treatment decisions.
Objective:
The European Consensus Document (ECD) defines critical ischaemia (CI) according to clinical (Fontaine) and blood pressure parameters. However, clinical symptoms may be non-specific and CI may exist without severely reduced blood pressures. This study prospectively investigated the additive value of transcutaneous oxygen tension (pO2) and toe blood pressure measurements to assess the presence of CI.
Methods:
Forty-nine patients with 65 legs clinically classified as Fontaine stages III (n = 23) and IV (n = 26) were studied. Ankle and toe systolic blood pressure and pO2 were measured to assess the presence of CI (cut-off values were 50, 30 and 30 mmHg, respectively). The surgeon was blinded for the toe pressure and pO2 results. The treatment received within 1 month after presentation was recorded as being either conservative or invasive (vascular surgery or PTA).
Results:
An ankle pressure of < or = 50 mmHg classified only 17% of the legs as having CI. By adding toe pressure and pO2, significantly more legs (63%; p < 0.0001) were classified as CI, of which 68% received invasive therapy. Forty-nine percent of the legs with an ankle pressure > 50 mmHg were treated invasively, whereas only 32% of the legs classified as not having CI by means of toe pressure and pO2 underwent invasive therapy. If the need for invasive treatment is used as the "gold standard" for the presence of CI, 54% of the legs would accurately be classified on the basis of the ankle blood pressure. The combination of toe pressure and pO2 would have yielded 71% and the ECD criteria 72% and accurately classified legs. The odds ratio for invasive therapy given a pO2 or toe pressure above the cut-off value was 14.
Conclusion:
Ankle blood pressure measurements have limited diagnostic value. Adding toe and/or oxygen pressures enhances the detection of CI requiring invasive therapy.